The present invention relates to an electronic feedback control method applicable to internal combustion engines provided with fuel injection valves and more particularly to an electronic feedback control method for controlling the quantity of fuel being injected into an internal combustion engine through a fuel injection valve, in which the flow rate of fuel injected through the fuel injection valve is detected for control of the fuel injection quantity.
A Diesel engine is conventionally provided with fuel injection valves formed of injection nozzles which are arranged to project into respective engine cylinders. Fuel is supplied to the fuel injection valves from a fuel injection pump or injection pumps through respective injection pipes and hence is injected into the respective engine cylinders through the valves. In a unit injector, fuel injection is carried out through a fuel injection valve by means of the pumping action of a fuel injection pump provided integrally with the fuel injection valve and formed of solenoid means or the like. The fuel injection quantity Q (mm.sup.3 /st) which is obtained by these fuel injection valves can be expressed by the following equation: EQU Q=CAt.sqroot.P
where:
C=constant, PA1 A=effective discharge area of the injection nozzle of a fuel injection valve, PA1 t=injection period, PA1 P=injection pressure (kg/cm.sup.2).
As is understood from the above equation, the fuel injection quantity can be controlled by varying any of the members A, t, P.
However, no control system has been proposed as yet which is adapted to control the fuel injection quantity by detecting the quantity of fuel injected through an injection nozzle and directly feeding the detected value back to the control section of the system.
In conventional fuel injection systems, the injection quantity is controlled in such an indirect manner that the position of the control rack engaging with pumping plungers in an in-line type fuel injection pump or the position of the control sleeve (or the regulating collar) engaging with a pumping plunger, in a distributor-type fuel injection pump is detected and the detected position is taken as a position corresponding to the actual injection quantity. However, according to such conventional arrangements, the actual injection quantity during each injection cannot be fed back to the control section with accuracy, making it impossible to control the injection quantity with accuracy. While in conventional unit injectors, it is difficult to detect the injection quantity since neither a control rack nor a control sleeve is provided in a conventional unit injector. Therefore, feedback control of the fuel injection quantity is little available with conventional unit injectors.